1. Field
Exemplary embodiments of the present invention relate to a semiconductor design technology and, more particularly, to an image sensing device and a read-out method of the same.
2. Description of the Related Art
Image sensing devices capture images using the photosensitive properties of semiconductors. Image sensing devices may be classified into charge coupled device (CCD) image sensors and complementary metal oxide semiconductor (CMOS) image sensors. The CMOS image sensors have come into widespread use. This is because CMOS image sensors allow for analog circuits and digital control circuits to be realized on a single integrated circuit (IC).
Image sensing devices may adopt a column-parallel scheme in order to improve read-out speed.
FIG. 1 illustrates an image sensing device 10 according to a prior art.
Referring to FIG. 1, the image sensing device 10 includes a pixel block 11 and a read-out block 13.
The pixel block 11 includes a plurality of pixels arranged in rows and columns. FIG. 1 exemplarily shows 8*2 pixels, which may be a part of the plurality of pixels in the pixel block 11. The pixel block 11 outputs pixel signals V<1:8> by rows based on the column-parallel scheme. For example, the pixel block 11 outputs the pixel signals V<1:8> from the pixels arranged in a first row ROW1, and subsequently outputs the pixel signals V<1:8> from the pixels arranged in a second row ROW2.
The read-out block 13 converts the pixel signals V<1:8> into digital signals D<1:8> in response to a source clock signal COL_CLK and sequentially outputs the digital signals D<1:8> to a common channel CH1.
However, there is a concern as follows in the image sensing device 10 having the aforementioned structure.
As the number of the pixels included in the pixel block 11 and the resolution of the image sensing device 10 increases, the number of row lines and column lines also increase. Consequently, the number of the pixel signals that have to be read out during a unit row time increases while the number of pixel signals from the read-out block 13 to the common channel CH1 during the limited unit row time is restricted. Thus, as the resolution of the image sensing device 10 increases, the pixel signals of the column lines take longer to be read out and may not finish within their allotted time.